So the data you have represents the height per week

Time (weeks) Height (cms)

3 4.6

4 5.8

7 9.4

So, In one week, the plant grew 5.8 - 4.6 = 1.2 cms

In the next 3 weeks the plant grew 9.4 - 5.8 = 3.6 cms

So in totality the plant growth was measured for 4 weeks and it grew by 4.8 cms (from 4.6 to 9.4)

So the growth rate per week is the ration of total increase/# of weeks

so we get the growth rate per week = 4.8/4 = 1.2 cms per week

Time (weeks) Height (cms)

3 4.6

4 5.8

7 9.4

So, In one week, the plant grew 5.8 - 4.6 = 1.2 cms

In the next 3 weeks the plant grew 9.4 - 5.8 = 3.6 cms

So in totality the plant growth was measured for 4 weeks and it grew by 4.8 cms (from 4.6 to 9.4)

So the growth rate per week is the ration of total increase/# of weeks

so we get the growth rate per week = 4.8/4 = 1.2 cms per week